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  <h2><a name="top">Logback error messages and their meanings</a></h2>
  

  <h3 class="doAnchor" name="null_CS">The contextSelector cannot be
  null in <code>StaticLoggerBinder</code>.  
  </h3>

  <p>An <code>IllegalStateException</code> is thrown when no
  ContextSelector could be set for logback's
  <code>StaticLoggerBinder</code>. In principle, this error can only
  occur when the context selector is expressly specified by the user,
  and when that context selector cannot not be instantiated correctly.
  </p>

  <p>It should not happen when you are using the default or JNDI
  context selectors.
  </p>
  

  <!-- =========================================================== -->
  <h3 class="doAnchor" name="layoutInsteadOfEncoder">This appender no
  longer admits a layout as a sub-component, set an encoder instead.
  </h3>

  <p>As of logback version 0.9.19, the <code>WriterAppender</code>
  class has been renamed as <code>OutputStreamAppender</code>, with
  <code>FileAppender</code> now sub-classing the
  latter. <code>OutputStreamAppender</code> and sub-classes now take
  an <code>Encoder</code> as a sub-component instead of a
  <code>Layout</code>.
  </p>

  <p>In practical terms, this means that configuration files need to
  be changed</p>
  
  <p class="red bold">from (DEPRECATED)</p>
  
  <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.FileAppender">
  &lt;file>testFile.log&lt;/file>
  ...
  &lt;layout class="ch.qos.logback.classic.PatternLayout">
    &lt;pattern>%msg%n&lt;/pattern>
  &lt;/layout>
&lt;/appender>   </pre>

  <p class="red bold">or the shorter equivalent (DEPRECATED)</p>

  <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.FileAppender">
  &lt;file>testFile.log&lt;/file>
  ...
  &lt;!-- layout are assigned the type ch.qos.logback.classic.PatternLayout by default -->
  &lt;layout>
    &lt;pattern>%msg%n&lt;/pattern>
  &lt;/layout>
&lt;/appender>   </pre>


  <p class="green bold">to (GOOD)</p>
    <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.FileAppender">
  &lt;file>testFile.log&lt;/file>
  ...
  &lt;encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
    &lt;pattern>%msg%n&lt;/pattern>
  &lt;/encoder>
&lt;/appender>   </pre>
 
  <p class="green bold">or the shorter equivalent (GOOD)</p>

   <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.FileAppender">
  &lt;file>testFile.log&lt;/file>
  ...
  &lt;!-- encoders are assigned the type 
       ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
  &lt;encoder>
    &lt;pattern>%msg%n&lt;/pattern>
  &lt;/encoder>
&lt;/appender>   </pre>


  <p>For layout type other than <code>PatternLayout</code>, for
  example <code>HTMLLayout</code>, your configuration files need to be
  changed
  </p>

  <p class="red bold">from (DEPRECATED)</p>

  <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.FileAppender">
  &lt;file>testFile.log&lt;/file>
  ...
  &lt;layout class="ch.qos.logback.classic.html.HTMLLayout">
    &lt;pattern>%msg%n&lt;/pattern>
  &lt;/layout>
&lt;/appender> </pre>


  <p class="green bold">to (GOOD)</p>
    <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.FileAppender">
  &lt;file>testFile.log&lt;/file>
  ...
  &lt;encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
    &lt;layout class="ch.qos.logback.classic.html.HTMLLayout">
      &lt;pattern>%msg%n&lt;/pattern>
    &lt;/layout>
  &lt;/encoder>
&lt;/appender> </pre>
  
  

  <p>We hope to make up for this inconvenience with cool new features
  which are only possible using encoders. <b>During a transition
  period, layouts passed as parameter will be automatically wrapped by
  an encoder so that configuration files in the old format (using a
  layout instead of encoder) will continue to work unmodified.</b>
  </p>

  
  

  <!-- =========================================================== -->

  <h3 class="doAnchor" name="socket_no_host">No remote host or address
  is set for <code>SocketAppender</code>
    
  </h3>

  <p>A remote host or address is mandatory for SocketAppender. </p>
  <p>You can specify the remote host in the configuration file
  as follows.
  </p>
  
  <pre class="prettyprint source">&lt;appender name="SOCKET"
  class="ch.qos.logback.classic.net.SocketAppender">
  ...
  &lt;remoteHost>127.0.0.1&lt;/remoteHost>
  ...
&lt;/appender&gt;</pre>


  

  <!-- ============================================================= -->

  <h3 class="doAnchor" name="socket_no_port">No remote port is set for
  <code>SocketAppender</code>    
  </h3>
    
  <p>A remote port is mandatory for SocketAppender.</p>
      
  <p>You can specify the remote port in the configuration file
  like this:
  </p>
      
  <pre class="prettyprint source">&lt;appender name="SOCKET" class=&quot;ch.qos.logback.classic.net.SocketAppender&quot;&gt;
  ...
  &lt;port>4560&lt;/port>
  ...
&lt;/appender&gt;</pre>
				


  

  <!-- ============================================================= -->

  <h3 class="doAnchor" name="smtp_no_layout">No <code>Layout</code> is
  set for SMTPAppender
  </h3>

  <p>A <code>Layout</code> is mandatory for
  <code>SMTPAppender</code>. It allows SMTPAppender to format logging
  events before sending an email.
  </p>
      
  <p>You can specify the <code>Layout</code> in a configuration file
  as follows:
  </p>
      
  <pre class="prettyprint source">&lt;appender name=&quot;SMTP&quot; class=&quot;ch.qos.logback.classic.net.SMTPAppender&quot;&gt;
  ...
  &lt;layout class=&quot;ch.qos.logback.classic.PatternLayout&quot;&gt;
    &lt;pattern>%date [%thread] %-5level %logger - %msg%n&quot;&gt;&lt;/pattern>
  &lt;/layout&gt;
  ...
&lt;/appender&gt;</pre>
      
  <p>SMTPAppender is known to work well with <a
  href="manual/layouts.html#ClassicPatternLayout">PatternLayout</a>
  and <a
  href="manual/layouts.html#ClassicHTMLLayout">HTMLLayout</a>.
  </p>


  
      
  <!-- ============================================================= -->

  <h3 class="doAnchor" name="sbtp_size_format">Specified number is not
  in proper int form, or not expected format.    
  </h3>
    
  <p>When you specify the MaxFileSize to be used by the
  SizeBasedRollingPolicy, logback expects a rather precise
  format:
  </p>
  
  <ul>
    <li>The number has to be an integer</li>
    <li>You can add 'KB', 'MB' or 'GB' after the number.
    </li>
  </ul>
      
  <p>Here are some correct values: 500KB, 15MB, 2GB.</p>
  
  
      
  <!-- ============================================================= -->

  <h3 class="doAnchor" name="rfa_no_tp">No
  <code>TriggeringPolicy</code> was set for the
  <code>RollingFileAppender</code>.
    
  </h3>
    
  <p>The <code>RollingFileAppender</code> must be set up with a
  <code>TriggeringPolicy</code>. It permits the Appender to know when
  the rollover must be activated.
  </p>
  
  <p>To find more information about <code>TriggeringPolicy</code>
  objects, please read the following javadocs:
  </p>
  
  <ul>
    <li>
      <a
       href="manual/appenders.html#SizeBasedTriggeringPolicy"><code>SizeBasedTriggeringPolicy</code>
      </a>
    </li>
    <li>
      <a
      href="manual/appenders.html#TimeBasedRollingPolicy"><code>TimeBasedRollingPolicy</code>
      </a>
    </li>
  </ul>
  
  <p>Please note that the <code>TimeBasedRollingPolicy</code>
  is a TriggeringPolicy <em>and</em> and
  <code>RollingPolicy</code> at the same time.
  </p>
      
  <!-- ============================================================= -->

  <h3 class="doAnchor" name="#sat_missing_integer_token">Missing
  integer token, that is %i, in FileNamePattern [...].
    
  </h3>
  
  <p>The %i conversion token is mandatory for <a
  href="manual/appenders.html#SizeAndTimeBasedFNATP">size and time
  based archiving</a>. In case the %i token is missing,
  <code>SizeAndTimeBasedFNATP</code> attached to
  <code>RollingFileAppender</code> will detect the omission and will
  not start.
  </p>

      
  <!-- ============================================================= -->

  <h3 class="doAnchor" name="rfa_no_rp">No <code>RollingPolicy</code>
  was set for the <code>RollingFileAppender</code>.    
  </h3>
  
  <p>The <code>RollingFileAppender</code> must be set up with
  a <code>RollingPolicy</code>. It permits the Appender to
  know what to do when a rollover is requested.
  </p>
    
  <p>To find more information about <code>RollingPolicy</code>
  objects, please read the following javadocs:
  </p>
    
  <ul>
    <li>
      <a href="apidocs/ch/qos/logback/core/rolling/FixedWindowRollingPolicy.html">
        <code>FixedWindowRollingPolicy</code>
      </a>
    </li>
    <li>
      <a href="apidocs/ch/qos/logback/core/rolling/TimeBasedRollingPolicy.html">
        <code>TimeBasedRollingPolicy</code>
      </a>
    </li>
  </ul>
  
  <p>Please note that the <code>TimeBasedRollingPolicy</code> is a
  <code>TriggeringPolicy</code> <em>and</em> and RollingPolicy at
  the same time.
  </p>
  
  
  

  <!-- ============================================================= -->
  <h3 class="doAnchor" name="tbr_fnp_not_set">The <span
  class="option">FileNamePattern</span> property is mandatory for both
  <code>TimeBasedRollingPolicy</code> and
  <code>FixedWindowRollingPolicy</code>.    
  </h3>

  
  <p>The <span class="option">FileNamePattern</span> property for both
  <code>TimeBasedRollingPolicy</code> and
  <code>FixedWindowRollingPolicy</code> is mandatory.
  </p>
  
  <p>Please refer to the documentation of <a
  href="manual/appenders.html#TimeBasedRollingPolicy">TimeBasedRollingPolicy</a>
  and <a
  href="manual/appenders.html#FixedWindowRollingPolicy">FixedWindowRollingPolicy</a> for
  examples.
  </p>


  

  <!-- ============================================================= -->
  <h3 class="doAnchor" name="rfa_file_after">The <span
  class="option">File</span> property must be set before any rolling
  policy or triggering policy.
    
  </h3>

  <p>The <span class="option">File</span> property, if present, must
  be placed before any rolling policy or triggering policy. Thus, in a
  configuration file, the <span class="option">File</span> property,
  if present, must be declared declared before any rolling policy or
  triggering policy declarations.
  </p>

  <!-- ============================================================= -->  

  <h3 class="doAnchor" name="rfa_collision"><span
  class="option">File</span> property collides with <span
  class="option">fileNamePattern</span>. Aborting.
  </h3>

  <p>When the <span class="option">file</span> property matches the
  regular expression defined by <span
  class="option">fileNamePattern</span>, there is a risk of
  collision. A collision occurs when the active log file as defined by
  the <span class="option">file</span> property has the same path as
  an existing log archive. Such a collision will result in the log
  archive being overwritten.
  </p>

  <p>As such, in case <span class="option">file</span> property
  matches the regular expression defined by <span
  class="option">fileNamePattern</span>, in order to avoid data loss,
  <code>RollingFileAppender</code> will emit an error message and
  refuse to start.</p>

  <!-- ============================================================= -->  

  <h3 class="doAnchor" name="rfa_collision_in_dateFormat">The date
  format in <span class="option">fileNamePattern</span> will result in
  collisions in the names of archived log files.
  </h3>

  <p>This error message is output when the date time pattern in the %d
  token within the <span class="option">fileNamePattern</span> is not
  collision free. For example, the following
  code>fileNamePattern</code> will result in the same log archive
  every day of the week after the first week of the month.
  </p>

  <pre class="source">myapp-%d{yyyy-MM-<span class="bold red">uu</span>}.log.zip</pre>

  <p>As such collisions will result in log data loss,
  <code>RollingFileAppender</code> will check for a variety of such
  possible collisions and will not start if any collisions are
  detected.</p>

  <!-- ============================================================= -->  

  <h3 class="doAnchor" name="earlier_fa_collision"><span
  class="option">File</span>/<span
  class="option">FileNamePattern</span> option has the same value "..." as
  that given for appender [...] defined earlier.
  </h3>


  <p>If a <code>FileAppender</code>/<code>RollingFileAppender</code>
  defined earlier has the same <span class="option">File</span> option
  as the current appender, then those two appenders are in collision
  as <code>FileAppender</code> instances cannot share the same output
  target. To prevent loss of data, the current appender will not
  start. Make sure that each appender has a unique <span
  class="option">File</span> option.
  </p>

  <p>By analogy the same restriction applies to the <span
  class="option">FileNamePattern</span> option of
  RollingFileAppender. Make sure that each RollingFileAppender has a
  unique <span class="option">FileNamePattern</span> option</p>
  
  <!-- =============================================================
       -->
  <h3 class="doAnchor" name="renamingError">Failed to rename file [x]
  as [y].</h3>

  <b>On Windows</b>

  <p>On the Windows platform a log file cannot be renamed if there are
  handles referencing it. For example, when the file is read by
  another process such as <code>less</code>, <code>tail</code>,
  etc. During application hot-redeployment, the old instance of the
  application will have open references to log files until the old
  instance is completely shutdown or until the <code>stop()</code>
  method on its <a
  href="apidocs/ch/qos/logback/classic/LoggerContext.html"><code>LoggerContext</code></a>
  is invoked.
  </p>

  <p><a
  href="http://technet.microsoft.com/en-us/sysinternals/bb896653">Process
  Explorer</a> can help you locate the processes which reference a
  given file (Find -&gt; Find Handle or DLL). On Linux, you can use
  the <code><a href="http://www.manpagez.com/man/8/lsof/">lsof </a>
  <em>pathToFile</em></code> command to find which process has the
  file given by <em>pathToFile</em> open. </p>

  <p>Rolling might also fail due to incorrect file permission
  settings. On windows, renaming a file requires the "modify"
  permission which is different than the permission to "write" to the
  file.</p>

  <p class="highlight">File rename operations during rollover can be
  avoided altogether by omitting the <span class="option">file</span>
  property in RollingFileAppender.</p>

  <p>In practice, it can be hard to set the right permissions or to
  ensure that there are no file handle references to log files.</p>

  <p>Under many circumstances, it can be more robust to avoid file
  renaming during rollover altogether. This is as easy as omitting the
  <span class="option">file</span> property in
  <code>RollingFileAppender</code>, as shown in the next configuration
  snippet.
  </p>

  <pre class="prettyprint source">&lt;appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
  <b>&lt;!-- <span class="option">file</span> property left unset/blank --></b>
  &lt;rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
    &lt;fileNamePattern>mylog.%d{yyyy-MM-dd}.log&lt;/fileNamePattern>
  &lt;/rollingPolicy>

  &lt;encoder>
    &lt;pattern>%relative [%thread] %level %logger - %msg%n&lt;/pattern>
  &lt;/encoder>
&lt;/appender></pre>

   <p>Note that for <code>FixedWindowRollingPolicy</code>, the <span
   class="option">file</span> property is mandatory.
   </p>
 
   <h4 class="doAnchor" name="renamingErrorOnUnix">On Unix-*</h4>
  
   <p>On the Unix platform, the basic/quick rename method supplied by
   the JDK does not work if the source and target files are located on
   different file systems. In order to deal with this contingency,
   logback will resort to renaming by copying if all of the following
   three conditions are met:</p>

   <ol>
     <li>quick renaming fails, </li>
     <li>source and destination files for the rename are on different
     file systems,
     </li>

     <li>the host JVM platform runs Java 7 or later.</li>
   </ol>

   <p>The code for determining the file system of a file requires Java
   7. No rename by copying will be performed on Java 6 or earlier.</p>
   
   <p>As explained in the Windows section above, renaming can be
   avoided altogether by omitting the <span class="option">file</span>
   property.
   </p>

  <!-- ============================================================= -->
  <h3 class="doAnchor" name="fwrp_parentFileName_not_set">The <span
  class="option">File</span> property must be set before
  <code>FixedWindowRollingPolicy</code>    
  </h3>

  <p>The <span class="option">File</span> property is mandatory with
  <code>FixedWindowRollingPolicy</code>. Moreover, the <span
  class="option">File</span> option must be set before the
  <code>FixedWindowRollingPolicy</code> element.
  </p>
      
  <p>Refer to the logback manual on
  <a href="manual/appenders.html#FixedWindowRollingPolicy">
    FixedWindowRollingPolicy </a> for more information.
  </p>
			
  
  <!-- ============================================================= -->
  <h3 class="doAnchor" name="tbr_fnp_prudent_unsupported">Prudent mode
  is not supported with <code>FixedWindowRollingPolicy</code>.
  </h3>

  <p>Given that <code>FixedWindowRollingPolicy</code> performs
  multiple file rename operations during roll over, and that these
  operations cannot be guaranteed to be safe in a multi-JVM context,
  prudent mode is not allowed in conjunction with a
  <code>FixedWindowRollingPolicy</code>.
  </p>

  
  
  <!-- ============================================================= -->
  <h3 class="doAnchor" name="syslog_layout">SyslogAppender does not
  admit a layout.
  </h3>


  <p>Given that the format of a syslog request follows strict rules,
  you cannot freely specify the layout to be used with
  SyslogAppender. However, you can use <span
  class="option">SuffixPattern</span> option instead to influence the
  contents of the message sent to the syslog daemon.
  </p>
  
  <p>For more information on SyslogAppender please refer to the <a
  href="manual/appenders.html#SyslogAppender">its documentation.</a>
  </p>

  

  <!-- ============================================================= -->
  <h3 class="doAnchor" name="1andOnly1">Only and only one appender can
  be nested the &lt;sift> element in
  <code>SiftingAppender</code>.</h3>
  
  <p>SiftingAppender admits one and only one nested appender. 
  </p>
  

  <!-- ============================================================= -->
  <h3 class="doAnchor" name="ifJanino">Could not find Janino library
  on the class path. Skipping conditional processing.
  </h3>
  
  <p><a href="manual/configuration.html#conditional">Conditional
  processing</a> in configuration files requires the <a
  href="http://docs.codehaus.org/display/JANINO/Home">Janino
  library</a>.  See the <a href="setup.html#janino">setup
  instructions</a> for adding Janino to your class path.
  </p>

  <!-- ============================================================= -->
  <h3 class="doAnchor" name="block">As of logback version 0.9.28,
  JaninoEventEvaluator expects Java blocks.
  </h3>

  <p>As of logback version 0.9.28, JaninoEvaluator expects Java
  "block", i.e. the body of a method. In previous versions only
  boolean expressions were allowed. For backward compatibility
  reasons, whenever logback sees a boolean expression it will attempt
  to convert it to a block by prefixing the expression with "return"
  and suffixing it with a semicolon.
  </p>

  <p>Boolean expressions can quickly become hairy. For example, the
  following boolean expression is rather difficult to grok.
</p>

  <pre class="prettyprint source"> !logger.startsWith("org.apache.http")
  ||
  ( logger.equals("org.apache.http.wire")  &amp;&amp;
       (mdc != null &amp;&amp; mdc.get("entity") != null
         &amp;&amp;
       ((String) mdc.get("entity")).contains("someSpecialValue"))
       &amp;&amp;
     !message.contains("someSecret")
  )</pre>

  <p>whereas as its Java block equivalent is considerably easier to
  follow.</p>

<pre class="prettyprint source">if(logger.startsWith("org.apache.http"))
  return true;

if(mdc == null || mdc.get("entity") == null)
  return false;

String payee = (String) mdc.get("entity");

if(logger.equals("org.apache.http.wire") &amp;&amp;
  payee.contains("someSpecialValue") &amp;&amp;
  !message.contains("someSecret")) {
  return true;
}

return false;</pre>

   <p>
   </p>

     <!-- ============================================================= -->
   <h3 class="doAnchor" name="param">The &lt;param&gt; element is
   deprecated in favor of a more direct syntax.
   </h3>


   <p class="red bold">Instead of writing (DEPRECATED)</p>  
   
   <pre class="prettyprint source">
    &lt;appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"&gt;
      &lt;encoder>
        &lt;<b>param name="pattern" value="%logger- %msg %n"/&gt;</b>
      &lt;/encoder>
    &lt;/appender>
   </pre>

   <p class="green bold">prefer the direct form (GOOD)

   <pre class="prettyprint source">
    &lt;appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
      &lt;encoder>
        <b>&lt;pattern>%logger - %msg %n&lt;/pattern></b>
      &lt;/encoder>
    &lt;/appender>
   </pre>

   <!-- ============================================================= -->
   <h3 class="doAnchor" name="missingRightParenthesis">In a conversion
   pattern, opened parenthesis must be closed.
   </h3>
   
   <p>In conversion patterns, <a
   href="manual/layouts.html#Parentheses">parentheses are special</a>
   because they are treated as grouping tokens. If a parenthesis
   character needs to be viewed as a literal, it needs to be escaped
   by preceding each parenthesis with a backslash. As in,
   <b>\(</b>%d{HH:mm:ss.SSS} [%thread]<b>\) </b>.
   </p>
  

   <!-- ============================================================= -->
   <h3 class="doAnchor" name="appender_order">Appenders must be
   definied before they are referenced.
   </h3>
   
   <p>In a configuration file, at the point where an appender is
   referenced by name, it must be defined earlier in the configuration
   file. Referencing an appender defined later in the file is not
   allowed. Below are examples of correct and incorrect order of
   definition and referece.
   </p>


  <p>Below is an example of a correct ordering, where appender
  definition precedes references made to it.
  </p>

  <p class="green bold">CORRECT ORDER</p>
  <pre class="prettyprint source">&lt;configuration>
  <b>&lt;!-- definition of appender STDOUT --></b>
  &lt;appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    &lt;encoder>
      &lt;pattern>%-4relative [%thread] %-5level %logger{35} - %msg %n&lt;/pattern>
    &lt;/encoder>
  &lt;/appender>

  &lt;root level="DEBUG">
    &lt;!-- appender referenced after it is defined -->
    <b class="big">&lt;appender-ref ref="STDOUT"/></b>
  &lt;/root> 
&lt;/configuration></pre>

  <p>Below is an example of an incorrect ordering, where appender
  definition follows references made to it.
  </p>

   <p class="red bold">INCORRECT ORDER</p>
   <pre class="prettyprint source">&lt;configuration>
  &lt;root level="DEBUG">
    &lt;!-- appender INCORRECTLY referenced before it is defined -->
    <b class="big">&lt;appender-ref ref="STDOUT"/></b>
  &lt;/root>

  <b>&lt;!-- definition of appender STDOUT --></b>
  &lt;appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    &lt;encoder>
      &lt;pattern>%-4relative [%thread] %-5level %logger{35} - %msg %n&lt;/pattern>
    &lt;/encoder>
  &lt;/appender>
&lt;/configuration>
   </pre>

 
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